User's Manual

www.vyyo.com
Configuration Overview – p. 23
First, the modem searches for a signal at its preprogrammed Downstream
Frequency. Once having locked to that downstream channel, the modem
receives upstream channel descriptors (UCDs) from the WMTS that describe the
available upstream channels.
NOTE: The WMTS must be configured to construct the
UCDs so that they correspond to the site preplan. Use
the Vyyo Configuration Tool to accomplish this if any
changes are required.
The modem then enters a protocol exchange that requires data be transmitted
from the modem to the WMTS via an Upstream Channel using its associated
Channel ID (designating the physical interface on the RF Interface card), and the
correct frequency, modulation and bandwidth or symbol rate.
NOTE: A modem configuration file which respecifies
these parameters is downloaded to the modem after
“ranging” (described below) is complete . This file is also
referred to as the modem “boot” file. All further
communication done by the modem uses the parameters
specified in this file. The modem configuration file is
modified using the CMconfigFileEditor tool.
This protocol exchange allows the modem to ‘range’ (adjust its timing and power
level so that it can work successfully with all of the other modems on line at this
time.). After the ranging is finished, the modem has successfully established
physical layer and Link or MAC layer connectivity with the WMTS. The WMTS is
now capable of sending MAC layer packets such as DHCP and ARP requests
required to complete the registration process.
2.4 IP Layer
Your System Engineer must devise a Network IP Plan. This is required in order
to assign IP addresses to the WMTS and all the modems on the network. It must
include the IP address of all the servers as well as the network mask and other
network parameters.
After connectivity is established at the DOCSIS layer (discussed in Section 2.3
DOCSIS Layer ), the modem is assigned to an IP address by using DHCP
(Dynamic Host Control Protocol.) If using the ipLease tool as the DHCP Server,
this is usually a static IP address defined in the DHCP setup file (CM.SRC.) This
file binds the modem's MAC address to a particular fixed IP address. If using
Windows 2000 Server Edition this binding is accomplished using its DHCP
Administrative Tool, which may be installed at the user’s option using the “netsh”
command (follow the instructions provided with your server).
The DHCP server grants the “lease” on the IP address to the modem (i.e., tells
the modem which IP address to use). The granted IP address is for SNMP
connectivity within the Vyyo system; it is not offered as a public IPaddress to
Vyyo equipment. However, if desired this can be done using the customer PC or
Router as the modem will behave as Layer 2 bridge device.